1. Field of the Invention
The present invention relates to an illuminance measurement apparatus, exposure apparatus, and exposure method, more particularly relates to an illuminance measurement apparatus used for measuring the illuminance of illumination light irradiated through a projection optical system provided in an exposure apparatus, illumination distribution in a region irradiated by the illumination light, etc., an exposure apparatus provided with such an illuminance measurement apparatus, and an exposure method using such an illuminance measurement apparatus.
2. Description of the Related Art
When producing a semiconductor device, a liquid crystal display device, or other device, use is made of an exposure apparatus for transfer of a pattern drawn on a mask or reticle (hereinafter also referred to all together as a xe2x80x9cmaskxe2x80x9d) or other master on to a semiconductor wafer or glass plate coated with a resist or other photosensitive substrate. To form a fine pattern on a photosensitive substrate using an exposure apparatus, it is necessary to strictly manage the illuminance of the illumination light emitted from an excimer laser or mercury lamp or other light source. Therefore, the exposure apparatus is provided with an illuminance measurement apparatus on the stage carrying the photosensitive substrate.
An illuminance measurement apparatus is generally configured by a light receiving element arranged in a chassis. The chassis is a housing formed at its top surface with a light receiving aperture. The light receiving element is set at a position where its light receiving surface corresponds to the light receiving aperture of the chassis, receives the exposure light entering from the light receiving aperture, and outputs an electrical signal corresponding to the illuminance to the outside through a wire etc. Note that an electrical board (printed circuit board) is sometimes also provided inside the chassis. In this case, the light receiving element is mounted on the electrical board. The illuminance of the illumination light is measured before transferring the pattern formed on the mask to the photosensitive substrate. By moving the stage in the in-plane direction of the stage, the light receiving aperture is arranged inside the region illuminated by the exposure light for measurement.
Such an illuminance measurement apparatus is adjusted by a high accuracy so that the height position of the light receiving aperture is in register with the surface of the photosensitive substrate and arranged on the stage carrying the photosensitive substrate. Here, the height position of the light receiving aperture is brought into register with the surface of the photosensitive substrate by a high precision so as to accurately measure the actual amount of exposure when transferring an image of a pattern formed on the mask to the photosensitive substrate. An image of the pattern formed on the mask is transferred to the photosensitive substrate in a state with the height position of the surface of the photosensitive substrate in register with an image plane of the projection optical system.
A reference board having a surface formed with fiducial marks etc. in register with the surface of the photosensitive substrate is provided on the stage. Detection light is irradiated toward the reference board and the reflected light received to find the height position of the reference board and the position of the stage in the height direction is adjusted so that the height position of the reference board is in register with the image plane of the projection optical system, assuming that the height positions of the reference board and light receiving aperture are in register, so that the light receiving aperture is in register with the image plane of the projection optical system.
If the height position of the reference board and the height position of the light receiving aperture are offset from each other, however, the measurement is performed in a state with the light receiving aperture defocused relative to the image plane of the projection optical system and therefore the illuminance or illumination distribution cannot be measured accurately. Therefore, to prevent this inconvenience, it is necessary to set the machining precision high when producing the illuminance measurement apparatus or mounting surface of the stage and to precisely mechanically adjust the height position of the light receiving aperture to strictly be in register with the height position of the reference board.
To bring the height position of the surface of the photosensitive substrate (height position of reference board) and height position of the light receiving aperture formed in the illuminance measurement apparatus into strict register with each other in this way, it is necessary to produce the illuminance measurement apparatus and the mounting surface of the stage with a high processing precision, so a large number of steps were required for machining and assembling the components and the cost became high.
Further, the illuminance measurement apparatus is not placed on the stage at all times. It is attached to the stage when measuring the illuminance of the illumination light before transferring the image of the pattern formed on the mask to the photosensitive substrate. Therefore, fine mechanical adjustment becomes necessary so that the height position of the light receiving aperture becomes accurately in register with the height position of the reference board at the time of mounting. Careful attention is required in the work. Due to the structure of the apparatus, the work is difficult. Along with this, a long time is required for the work. This becomes one reason lowering the throughput. Further, if foreign matter adheres to the back surface of the illuminance measurement apparatus or the mounting surface of the stage, the reproducibility of mounting of the illuminance measurement apparatus deteriorates, the chassis surface where the light receiving aperture is formed becomes tilted, and the precision of setting of the height position falls. If it is not possible to bring the height positions of the light receiving aperture and reference board into accurate register, it is not possible to accurately measure the illuminance and not possible to transfer a pattern with a high precision.
Therefore, an object of the present invention is to improve the accurately of measurement of the illuminance of exposure light irradiated on a substrate, facilitate processing and assembly, and speed up and facilitate mounting work and thereby reduce costs and improve throughput.
According to a first aspect of the present invention, there is provided an illuminance measurement apparatus having a chassis having a detection surface formed with an aperture and a light receiving element with a light receiving surface arranged at a position corresponding to the aperture in the chassis, wherein the chassis is provided with a reflection surface for detection light for detecting at least one of the position and posture of the detection surface.
According to the present invention, since the chassis having the detection surface formed with the aperture is provided with a reflection surface of the detection light, the relative positional relationship between the detection surface and the reflection surface is fixed unambiguously. Therefore, it becomes possible to adjust the position (and/or posture) of the detection surface based on the results of detection of the reflection surface obtained by irradiating detection light to the reflection surface. As a result, it becomes possible to detect the illuminance with a high precision. Further, since the relative positional relationship between the reflection surface and detection surface does not change, there is less of a need to produce or mount the illuminance measurement apparatus with a high precision than in the past and as a result it is possible to relax the requirement on manufacturing tolerance or mounting tolerance of the illuminance measurement apparatus, reduce the cost, and improve the throughput.
Here, it is possible to provide the reflection surface adjoining the detection surface so that the normal of the reflection surface becomes substantially parallel to the normal of the detection surface. In this case, from the viewpoint of facilitating manufacture or reducing cost etc., it is possible to provide the reflection surface in substantially the same plane as the detection surface or to arrange the reflection surface to be offset relative to the detection surface in the normal direction of the detection surface.
According to a second aspect of the present invention, there is provided an exposure apparatus for transferring a pattern of a mask on to a substrate by exposure light, the exposure apparatus provided with a stage for holding the substrate and adjusting at least one of a position and posture of the substrate, a detection device for irradiating detection light toward an object on the stage and receiving the light reflected at the object to detect at least one of the position and posture of the object, an illuminance measurement apparatus, having a chassis having a detection surface formed with an aperture through which the exposure light enters, a light receiving element having a light receiving surface provided at a position corresponding to the aperture in the chassis, and a reflection surface for reflecting the detection light provided on the chassis, and mounted on the stage, and a control device for controlling the stage so that the detection surface becomes in register with a predetermined reference based on the result of detection of the detection device when irradiating the detection light to the reflection surface.
According to the present invention, the chassis is provided with a reflection surface of detection light for detecting the position (and/or posture) of the detection surface and the position (and/or posture) of the detection surface is adjusted by controlling the stage based on the result of detection of the reflection surface obtained by irradiating detection light on that reflection surface. Since the reflection surface and the detection surface are formed in the same chassis, the relative positional relationship between the reflection surface and the detection surface is fixed unambiguously and does not change, so it becomes possible to measure the illuminance at a high precision and fast speed without that much reliance on the mechanical precision of the illuminance measurement apparatus or the mounting precision on the stage. Therefore, it becomes possible to transfer and form a high precision pattern on a photosensitive substrate by a high throughput. As a result, it becomes possible to produce a high quality, high reliability microdevice etc. The cost of production of such a microdevice therefore also can be reduced.
Here, the control device may have a storage device storing data showing the relative positional relationship between the reflection surface and the detection surface. For example, when the reflection surface is arranged offset from the detection surface in the normal direction of the detection surface, the control device can correct the offset by reading the data indicating the relative positional relationship between the reflection surface and detection surface from the storage device, so even if there is a limit to the positional relationship between the reflection surface and the detection surface, it is possible to measure the illuminance of the exposure light at a high precision. Further, by a main control system 16 outputting a control signal to the illumination light source 1 to change the control parameters, it becomes possible to continuously finely adjust the intensity of the illumination light IL. Note that the control parameters include the voltage or power given to the light source etc.
According to a third aspect of the present invention, there is provided an exposure method for transferring a pattern of a mask on to a substrate by exposure light, the exposure method comprising the steps of mounting an illuminance measurement apparatus having a chassis having a detection surface formed with an aperture through which the exposure light enters, a light receiving device having a light receiving surface provided at a position corresponding to the aperture in the chassis, and a reflection surface provided on the chassis on a stage for holding the substrate and adjusting at least one of a position and posture of the substrate, irradiating detection light toward the reflection surface and receiving the light reflected at the reflection surface to detect at least one of the position and posture of the reflection surface, controlling the stage so that the detection surface becomes in register with a predetermined reference based on the result of detection when irradiating the detection light to the reflection surface, irradiating the exposure light to the detection surface and measuring the illuminance of the exposure light, and adjusting the illuminance of the exposure light and exposing the substrate based on the results of measurement when irradiating the exposure light on the detection surface.
Note that the illuminance measurement apparatus, exposure apparatus, and exposure method of the present invention cover not only the case where the detection surface formed with the aperture and the light receiving surface of the illuminance measurement apparatus are separated in position, but also the case where they are at the same position. For example, there are cases where the detection surface formed with the aperture is formed integrally on the light receiving surface.
According to a fourth aspect of the present invention, there is provided a method of exposure of a second object by exposure light through a first object having a pattern, the exposure method comprising arranging a measurement device having a light receiving surface struck by the exposure light on a movable member able to adjust at least one of the position and posture of the same, detecting information relating to at least one of the position and posture of the detection surface of the measurement device, and driving the movable member to bring the detection surface into register with a predetermined reference based on the information so that the measurement device may detect the exposure light. In this case, to detect that information, it is possible to irradiate detection light to a reflection surface of the measurement device arranged in a predetermined positional relationship with the detection surface and receive the light reflected from that reflection surface.